BALTIMORE — For a long time now, hydrogen has been the fuel of the future. A new idea for extracting hydrogen from water might help that future arrive a little sooner.
Today, producing hydrogen requires burning fossil fuels or using water-splitting catalysts that work relatively inefficiently, says physicist Arvin Kakekhani of Yale University. But Kakekhani and Sohrab Ismail-Beigi, also at Yale, identified a strategy using materials known as ferroelectric oxides to catalytically separate hydrogen from oxygen more effectively.
Catalysis requires a surface that both grips a water molecule in order to split it and releases the hydrogen atoms separated in the process. Ordinary catalysts must compromise between these two competing qualities. But a ferroelectric substance such as lead titanate can be prepared so that heat can switch it from a state suitable for splitting to another state good at releasing, computer simulations showed. Researchers therefore should be able to design a cycle of states that extracts hydrogen efficiently, Kakekhani reported March 17 in a news conference at a meeting of the American Physical Society.
“It’s a conceptual study that should be experimentally confirmed,” he said. A report on the work was also published online March 8 in the Journal of Materials Chemistry A.
There must be something wrong with the guy who never leaves home, right? Maybe not — at least if that guy is a male spotted hyena. Males that stay with their birth clan, instead of taking off to join a new group, may simply be making a good choice, a new study suggests.
Spotted hyenas are a matriarchal society. Females are in charge. They rank higher than every male in the clan. And the females generally stay with the clan for their entire lives. But males face a choice when they reach two and a half years in age. They can stay with the clan, or they can leave and join a new clan.
Each choice has its pros and cons. Staying with the clan means that a male hyena keeps a place at the top of the male pecking order. He’ll probably have his mother around to help. But he’ll be limited in the number of females he can mate with, because many of the female hyenas won’t mate with him because they might be related. If he joins a new clan, the male hyena might have access to more females — and they might even be better than the ones in his home clan — but he’ll start with the lowest social rank and have to spend years fighting his way to the top.
Among most group-living mammal species, the guys that stay at home turn out to be losers, siring fewer offspring. But spotted hyenas, it appears, are an exception.
Eve Davidian of the Leibniz Institute for Zoo and Wildlife Research in Berlin and colleagues tracked 254 male spotted hyenas that lived in eight clans in Ngorongoro Crater in Tanzania throughout their lives, a study lasting 20 years. When these males reached the age of maturity, they left their clans to take a look at the other options available to them. Forty-one hyenas returned to their home clans, and 213 settled with new ones.
Even though the males that stayed at home probably had fewer potential breeding partners, they still managed to sire as many offspring as those males that left for greener pastures. Many mated at an earlier age, and they tended to mate with higher-ranking females than males that joined new clans. And both groups lived similar lengths of time, the researchers report March 18 in Science Advances.
The guys who stay at home, it seems, aren’t losers who couldn’t find better prospects elsewhere. They just found good enough prospects at home, where they are at the top of the social ladder — and have mom around to help them get access to food and females.
Seems like a good strategy — for hyenas, at least.
White dwarfs — the exposed cores of dead stars — are the last place astronomers expected to find an oxygen atmosphere. Yet that’s exactly what recently turned up, providing researchers a rare peek inside the core of a massive star and raising questions about how such an oddball could have formed.
Most stars die by gently casting the bulk of their gas into space, leaving behind a dense, hot core. Heavy elements such as carbon and oxygen sink to the core’s center while hydrogen and helium float to the surface. But a newly discovered white dwarf, about 1,200 light-years away in the constellation Draco, has no hydrogen or helium at its surface. Its atmosphere is instead dominated by oxygen, researchers report in the April 1 Science. “We only found one, so it is a rare event,” says study coauthor Kepler de Souza Oliveira Filho, an astronomer at the Federal University of Rio Grande do Sul in Porto Alegre, Brazil. But, he says, “every theory must be able to explain all events, even the rare ones.”
Hydrogen and helium blanket most white dwarfs, hiding what lies beneath. Here, astronomers have “a window into the core of a star that we didn’t have before,” says Patrick Dufour, an astrophysicist at the University of Montreal.
While oxygen dominates this white dwarf’s atmosphere, neon and magnesium come in second and third — a clue that the original star was much bigger than our sun. Big stars can crank up their core temperatures high enough to fuse progressively heavier elements. A star between about six and 10 times as massive as the sun ends up with a core made of mostly oxygen, neon and magnesium — precisely what Filho and colleagues found. But there’s a problem: Such a white dwarf should be a bit heavier than our sun, and this newly discovered misfit appears to have about half as much mass.
A nearby stellar companion could have siphoned gas off the dying star, starving the white dwarf of mass, the researchers suggest. Thermonuclear excavation during the star’s end game could also lead to an underweight white dwarf. If enough hydrogen piled up on the core, it might have triggered a runaway nuclear explosion that shaved off the white dwarf’s outer layers.
While plausible, it’s hard to see how that could remove half of the white dwarf’s mass, Dufour says. “That’s very strange,” he says. “It could work, but I doubt it would leave a low-mass white dwarf.” In 2007, Dufour and colleagues reported a similar strange sighting: several white dwarfs whose atmospheres were loaded with carbon instead of hydrogen and helium. Those also appeared to be missing some mass, he says, though the problem was found to lie not with the stars but with the mass estimates. The white dwarfs are heavier than initially thought, and Dufour now suspects that each one arose from a collision between two white dwarfs.
It’s too early to draw strong conclusions from a single oxygen-laden white dwarf. “There are lots of open questions before we can say that this changes our view of white dwarf evolution,” Dufour says. “This white dwarf might only be a freak…. Although often in science, it’s the exception that makes you understand a great deal later on.”
Antarctica’s meltdown could spur sea level rise well beyond current predictions. A new simulation of the continent’s thawing ice suggests that Antarctic melting alone will raise global sea levels by about 64 to 114 centimeters by 2100, scientists report in the March 31 Nature.
Adding Antarctic melt to other sources of sea level rise, such as the expansion of warming seawater and melting Greenland ice, the scientists predict that sea levels will rise 1.5 to 2.1 meters by the end of the century. That’s as much as double previous predictions that didn’t incorporate mechanisms that can expedite the Antarctic ice sheet’s collapse, though uncertainties remain, says study coauthor David Pollard, a paleoclimatologist at Penn State. Predicting future sea level rise requires understanding how the oceans rose in the past. Scientists often glean ancient sea level rise by reconstructing the locations of ancient coastlines. But these coastlines can be a slippery target: Forces such as tectonic activity can cause Earth’s surface to rise and fall, obscuring the effects of past sea level rise. Depending on how much uplift obfuscated ancient sea level records — ranging from no uplift to massive uplift — the new prediction of 21st century sea level rise can differ by 35 centimeters or more.
A separate study also highlights the challenges of factoring changing coastlines into sea level rise predictions. Researchers estimate online April 2 in Geophysical Research Letters that groundwater depletion has caused the coasts of California and India to rebound upward, counteracting sea level rise in those regions by about 0.4 millimeters per year.
“I really would be happier if we had the luxury of doing the research on this without bothering the public until we have 95 percent confidence in an answer,”says Penn State glaciologist Richard Alley, who was not involved in either study. “Any single forecast is notably uncertain, but if we continue warming the world rapidly, the most likely outcome is a major event of large and rapid sea level rise.”
Two warm periods, one about 125,000 years ago and another about 3 million years ago, were particularly useful for Pollard and coauthor Robert DeConto, a geoscientist at the University of Massachusetts Amherst. Those bouts of warming shrank Earth’s ice sheets and boosted sea levels by several meters. Pollard and DeConto used these sea level records to fine-tune a computer simulation of how climate change affects the Antarctic ice sheet. The researchers then applied their calibrated simulation to current climate conditions and projected sea level rise thousands of years into the future.
Assuming that society takes no actions to curb greenhouse gas emissions, the simulation predicts that Antarctic melting will accelerate around 2050 as rising temperatures destabilize several keystone glaciers in West Antarctica. After 2100, Antarctica’s contribution to sea level rise will exceed 4 centimeters a year — more than 10 times the current rate from all sources. Such severe sea level rise would reshape most of Earth’s coastlines, and the waters would rise even higher as time goes on, Pollard predicts. “Sea levels won’t peak until around 3,000 to 4,000 years from now,”he says. At that point, Antarctica will have raised global sea levels by about 20 meters.
The consequences of this long-term sea level rise will be dire, says Maureen Raymo, a marine geologist at Columbia University’s Lamont-Doherty Earth Observatory in Palisades, N.Y., who was not involved with the work. “I haven’t seen anyone mention the long, slowly unfolding refugee crisis that will only get worse as hundreds of millions [of people] are displaced worldwide,” she says.
Even top-caliber diamonds aren’t perfect. And their imperfections are finally settling a debate about the origins of the gem-quality diamonds used in jewelry.
Previously, scientists had an explanation only for how cloudy and impurity-ridden fibrous diamonds form. Those diamonds crystallize inside fluid pockets deep within the Earth that contain compounds called carbonates. Carbonate-containing impurities inside fibrous diamonds provide information about the diamonds’ origins. Gem diamonds typically don’t contain these impurities, so scientists argued over whether the gems formed under different conditions than fibrous diamonds. After an exhaustive hunt, geochemists have at last found microscopic impurities within gem-quality diamonds. These flaws suggest that pretty and ugly diamonds form from the same kinds of carbonate-containing fluids, the researchers report in the June 1 issue of Earth and Planetary Science Letters. The finding may also offer insights into the history of plate tectonics.
The work “gives us the first strong constraint on how gem diamonds grow,” says Thomas Stachel, a petrologist at the University of Alberta in Canada who was not involved in the research. “People had proposed various explanations for how these diamonds form, but it seems diamond formation is less diverse than we thought.”
Diamonds are made up of carbon atoms. At the pressures and temperatures found in the deep Earth, these carbon atoms can form a crystal structure. Rising magma then carries the crystals to the surface.
The type of diamonds prized for jewelry formed as early as 3.5 billion years ago. Fibrous diamonds date back only a few million years and formed more quickly. That quick creation trapped bits of surrounding material inside the crystal structure. Those inclusions suggest that these diamonds formed from the carbon atoms in carbonate-containing fluids. Gem-quality diamonds formed more slowly and usually don’t contain any inclusions. “That’s why they’re gem quality —there’s nothing in them,” says study coauthor Brooke Matat Jablon, a geochemist at the Hebrew University of Jerusalem. Jablon and geochemist Oded Navon, also at the Hebrew University, hunted for inclusions in diamond gemstones. The researchers finally found what they were looking for in diamonds that are symmetrical across a central boundary. As these diamonds grew, a microscopic inclusion would sometimes become trapped along the boundary. Using a beam of electrons, the researchers identified 32 inclusions in eight of 30 diamonds they examined. Twenty of those inclusions were the same carbonate-bearing fluids found in the fibrous diamonds. The finding suggests that while fibrous diamonds and gem-quality diamonds differ in age and price, they share common origins. “We’re coming full circle on the story,” Jablon says. “We can quiet a debate that has been raging in the field for a long time. Going forward, we can generally assume most diamonds crystalize the same way.”
A similar mechanism for creating older, gem-quality diamonds and younger, fibrous diamonds suggests that Earth has maintained diamond-forming conditions for billions of years, Stachel says. Carbonates are carried into Earth’s depths when tectonic plates subduct and sink into the planet’s interior. If ancient diamonds form from carbonates, plate tectonics could have already been churning the planet’s exterior 3.5 billion years ago, he says.
During mating season, a flamboyant fowl will raise his iridescent train, shake his wings and vibrate his fan. Such displays can go on for hours.
Biologist Roslyn Dakin of the University of British Columbia in Vancouver teamed with physicist Suzanne Kane of Haverford College in Pennsylvania and other collaborators to break down the basic biomechanics of this shimmy show, known as rattling. The team also investigated a related peacock move called shivering — a reshuffling of feathers akin to a dandy combing his hair — that occurs before females arrive. The researchers recorded feral peafowl (Pavo cristatus) in action with a high-speed video camera and studied feathers in the lab. Rattling birds literally shake their shorter, stiff tail feathers to strum their fanned-out train, making the train feathers vibrate at the same high frequency (25.6 hertz on average), the team reports April 27 in PLOS ONE. This frequency sweet spot generates a loud rustling noise — also part of the show. Although the scientists saw variety from bird to bird, individual peacocks tended to vibrate their feathers at a consistent frequency. Males with longer trains vibrated at slightly higher frequencies than those with shorter ones. Shivering involved lower-frequency feather vibrations than rattling.
Despite all this gyration, the eyespots stay still thanks to tiny hooks that lock the eyespot barbs together. “It isn’t just beautiful,” Kane explains. “It acts like a single mass at the top of the feather.”
Previous studies have shown that males with more iridescent eyespots have better game. High-frequency shimmying might be indicative of a male’s health or muscle power, Dakin says. But how the female perceives the total package remains to be studied. “One has to wonder what it’s like to be a female seeing this for the first time,” she says.
The historic El Niño event currently shaking up Earth’s weather rose like a phoenix from the hot remains of a failed 2014 El Niño, new research suggests.
In 2014, the scientific community buzzed about the possibility of a supersized El Niño as warm Pacific Ocean water sloshed eastward. That July, however, large winds pushed westward and halted the budding El Niño before it fully formed (SN: 11/1/14, p. 6). Those same winds also prevented the release of stored-up ocean heat, researchers report in a paper to be published in Geophysical Research Letters. In March 2015, that lingering heat gave the current El Niño a jump start toward the extreme, the researchers propose. The ongoing El Niño is among the three strongest on record (SN Online: 7/16/15); it has boosted rainfall in California, contributed to ocean coral bleaching and helped make 2015 the hottest year on record (SN: 2/20/16, p. 13). Such a once-in-a-generation El Niño would have been less likely without the failed 2014 event, says study coauthor Michael McPhaden, a physical oceanographer at the National Oceanic and Atmospheric Administration’s Pacific Marine Environmental Laboratory in Seattle.
“In a sense, we dodged a bullet in 2014 by not having a monster El Niño,” McPhaden says. “But that was short-lived, because the conditions that shut that developing El Niño down set up the big one in 2015.”
El Niños typically form every two to seven years when Pacific winds shift a large, near-surface pool of warm water eastward. That warm water then rises to the surface and releases its heat into the atmosphere, causing global shifts in storms, precipitation and temperatures.
The fizzled 2014 El Niño followed by a colossal event in 2015 is very unusual, McPhaden says. He and climate scientist Aaron Levine, also at NOAA’s Pacific Marine Environmental Laboratory, wondered if the sequence of events was just a coincidence. So the researchers looked at decades of El Niño climate data and ran computer simulations of various hypothetical El Niño events.
Under typical ocean conditions, the chances of a 2015 El Niño of any strength are about 27 percent, the researchers estimate. The remnant heat from the failed 2014 El Niño increased those odds to roughly 40 percent. Having a failed El Niño the previous year stacks the deck in favor of an El Niño, McPhaden and Levin conclude. But it “isn’t a guarantee,” Levine says. A similar aborted El Niño occurred in 1990, the researchers find. An El Niño formed the following year, but the event ended up being more modest than the current super El Niño. That’s in part because the eastward-blowing winds in 1991 were relatively weak, Levine says. Strong El Niños require strong winds, not just warm water, he adds.
Forecasting those winds is tricky because the winds and the warm water “are all part of the same system,” says Kevin Trenberth, a climate scientist at the National Center for Atmospheric Research in Boulder, Colo. Ocean heat can cause atmospheric changes that can in turn influence the winds. The new work provides insights, he says, “but it is far from complete.”
Packing on a few pounds may not be such a bad thing.
As a group, overweight people are living the longest nowadays, suggests an almost four-decade study in Denmark published May 10 in JAMA. And obese people seem to be at no higher risk of dying than those of normal weight. The new analysis fuels ongoing debate about what’s a healthy body mass index — especially in light of rising obesity rates (SN: 5/14/16, p. 5), improved heart health treatments and other factors influencing health and longevity. “This is a very carefully done study,” says Rexford Ahima, a physician who studies endocrine disorders at the University of Pennsylvania School of Medicine. The findings strengthen the notion that “BMI as a number alone may not be sufficient to predict health and risk of death. It has to be taken within context.” Ahima was not involved in the research but has analyzed previous studies urging a rethink of how BMI influences mortality.
Researchers screen for obesity by calculating BMI — a popular but fairly crude measurement of body fat reached by dividing a person’s weight in kilograms by the square of height in meters. People with BMIs between 18.5 and 24.9 are considered normal. A BMI between 25 and 29.9 is “overweight”; 30 and above is “obese.”
Many studies suggest that obese individuals face a higher risk of heart disease, stroke and other ills. But some analyses have found that heavier folks may not in fact be in such dire straits. In one study of type 2 diabetes patients, those with normal weight when diagnosed were more likely to die than those who were overweight or obese (SN: 9/8/12, p. 13). And a 2013 meta-analysis of 97 studies found that being overweight was associated with lower risk of death than having a normal BMI — a surprising finding that echoed a 2005 study by the same researchers.
In this new analysis, clinical biochemist Børge Nordestgaard of Copenhagen University Hospital and his team studied more than 100,000 adults. The three groups of white Danes, recruited about 15 years apart, reflected the general population in Copenhagen.
From 1976 to 2013, BMI associated with lowest risk of death increased from 23.7 to 27. That falls squarely in the overweight category. What’s more, obese individuals had the same mortality risk as people in the normal range, the analysis found. That trend held even when researchers took into account potentially confounding factors including age, sex, smoking and a history of cardiovascular disease or cancer. While some might misinterpret the study to mean “you can eat as much as you like,” this is not what the findings suggest, Nordestgaard says. Rather, the results indicate that people who are moderately overweight might not need to worry as much as they had in the past. That might be because better treatments are now available for high blood pressure, high cholesterol and other risk factors for heart disease, Nordestgaard speculates. “So maybe you can be overweight if you have [these conditions] treated.” But the study was not designed to address whether improved heart health care actually caused “healthy” BMI values to creep up over time.
It’s also unclear whether the results apply to other ethnic groups. A substantial fraction of Asians, for instance, develop type 2 diabetes and heart disease despite having BMIs lower than the existing cutoff point for being overweight.
The findings underscore the idea that a person’s BMI does not tell the whole story. While this measure is good for comparing populations, it is not as useful for evaluating individuals and their risk for disease and death, Ahima says. Interpreting an individual’s BMI depends on many other factors, including “whether you are man or woman, how much muscle you have, how physically fit you are and what diseases you have.”
Houseflies stretch their legs to land. Bumblebees hover, then slowly descend. Now, insect-sized flying robots have a way to stick the landing, too.
A tiny aerial bot about the size of a bee (nicknamed RoboBee) uses static electricity to cling to the underside of a leaf and perch on other materials, study coauthor Robert Wood of Harvard University and colleagues report in the May 20 Science.
RoboBee, a bot with shiny, flapping wings and four pinlike legs, is the first of its size that can fly, perch on a surface and then take off again. This energy-saving feat could one day extend mission time in search and rescue operations, the researchers say. For robots, tackling the problem of flight has been easier than figuring out how to land. “Engineers have been trying to build perching mechanisms for flying robots nearly as long as we have been creating flying robots,” Wood says. Researchers have had success with bigger, bird-sized bots (SN: 2/7/15, p. 18), but their landing mechanisms are tricky to scale down. For the microbot, Wood and colleagues wanted something simple: lightweight and without moving parts.
The team created an “electroadhesive” patch with electrodes that can be charged, letting the patch stick to different surfaces, like a balloon sticking to the wall after being rubbed on someone’s hair.
Switch the electrodes on and the patch, a circular disc on top of the robot, helps RoboBee hang out on overhanging pieces of glass or plywood, for example. Switch the electrodes off and the bot detaches, free to fly again. The sticky contraption lets RoboBee rest between flights: The bot used about a thousandth as much energy perching than hovering, the researchers found.
Painkillers in the opium family may actually make pain last longer. Morphine treatment after a nerve injury doubled the duration of pain in rats, scientists report the week of May 30 in the Proceedings of the National Academy of Sciences.
The results raise the troubling prospect that in addition to having unpleasant side effects and addictive potential, opioids such as OxyContin and Vicodin could actually extend some types of pain. If a similar effect is found in people, “it suggests that the treatment is actually contributing to the problem,” says study coauthor Peter Grace, a neuroscientist at the University of Colorado Boulder. Scientists have known that opioid-based drugs can cause heightened sensitivity to pain for some people, a condition called opioid-induced hyperalgesia. The new study shows that the effects linger weeks after use of the drugs is stopped. Male rats underwent surgery in which their sciatic nerves, which run down the hind legs, were squeezed with a stitch — a constriction that causes pain afterward. Ten days after surgery, rats received a five-day course of either morphine or saline.
Rats that didn’t receive morphine took about four weeks to start recovering, showing less sensitivity to a poke. Rats that got morphine took about eight weeks to show improvements — double the time. “That’s far bigger than we had anticipated,” Grace says. “We were definitely surprised by that.”
These experiments were done with male rats, but unpublished data indicate that morphine extends pain even longer in female rats, Grace says, results that fit with what’s known about differences in how males and females experience pain.
Longer-lasting pain in the rats came courtesy of an inflammatory response in the spinal cord. The immune system sees morphine as a threat, the researchers suspect, and responds by revving up inflammation through specialized cells called microglia. Experiments that shut down this process in microglia shortened the duration of the pain.
Many questions remain. Scientists don’t yet know if a similar immune reaction happens in people. Nor is it known whether all opioid-based painkillers would behave like morphine. Understanding the details of how the process works has important implications for doctors, many of whom may be unaware of opioids’ complex relationship with pain, says internal medicine physician Jonathan Chen of Stanford University School of Medicine. Clarity on how opioids influence pain could change doctors’ prescribing habits and encourage the search for better pain treatments, he says.
Grace points out that the experiments were done in genetically similar rats, and that people may have more varied responses to opioids. That variability might mean that not everyone would be at risk for such long-lasting pain, he says. “But clearly these data suggest that there may be a subset of people who might be in trouble.”
